arXiv subjects

Simon L. Cornish

Publications and source records attributed to Simon L. Cornish.

At least 55 records · Page 3Linked to original sources

arXiv2018

Production of ultracold Cs*Yb molecules by photoassociation

We report the production of ultracold heteronuclear Cs$^*$Yb molecules through one-photon photoassociation applied to an ultracold atomic mixture of Cs and Yb confined in an optical dipole trap. We use trap-loss spectroscopy to detect molecular states below the Cs($^{2}P_{1/2}$) + Yb($^{1}S_{0}$) asymptote. For $^{133}$Cs$^{174}$Yb, we observe 13 rovibrational states with binding energies up to $\sim$500 GHz. For each rovibrational state we observe two resonances associated with the Cs hyperfine structure and show that the hyperfine splitting in the diatomic molecule decreases for more deeply bound states. In addition, we produce ultracold fermionic $^{133}$Cs$^{173}$Yb and bosonic $^{133}$Cs$^{172}$Yb and $^{133}$Cs$^{170}$Yb molecules. From mass scaling, we determine the number of bound states supported by the 2(1/2) excited-state potential to be 154 or 155.

physics.atom-ph↗

arXiv2017

Spin-orbit coupled interferometry with ring-trapped Bose--Einstein condensates

We propose a method of atom-interferometry using a spinor Bose-Einstein condensate (BEC) with a time-varying magnetic field acting as a coherent beam-splitter. Our protocol creates long-lived superpositional counterflow states, which are of fundamental interest and can be made sensitive to both the Sagnac effect and magnetic fields on the sub-micro-G scale. We split a ring-trapped condensate, initially in the $m_f=0$ hyperfine state, into superpositions of internal $m_f=\pm1$ states and condensate superflow, which are spin-orbit coupled. After interrogation, relative phase accumulation can be inferred from a population transfer to the $m_f=\pm1$ states. The counterflow generation protocol is adiabatically deterministic and does not rely on coupling to additional optical fields or mechanical stirring techniques. Our protocol can maximise the classical Fisher information for any rotation, magnetic field, or interrigation time, and so has the maximum sensitivity available to uncorrelated particles. Precision can increase with the interrogation time, and so is limited only by the lifetime of the condensate.

cond-mat.quant-gas↗

arXiv2017

AC Stark Effect in Ultracold Polar RbCs Molecules

We investigate the effect of far-off-resonant trapping light on ultracold bosonic RbCs molecules. We use kHz-precision microwave spectroscopy to measure the differential AC Stark shifts between the ground and first excited rotational levels of the molecule with hyperfine-state resolution. We demonstrate through both experiment and theory that coupling between neighboring hyperfine states manifests in rich structure with many avoided crossings. This coupling may be tuned by rotating the polarization of the linearly polarized trapping light. A combination of spectroscopic and parametric heating measurements allows complete characterization of the molecular polarizability at a wavelength of 1550~nm in both the ground and first excited rotational states.

cond-mat.quant-gas↗

arXiv2017

Interspecies thermalization in an ultracold mixture of Cs and Yb in an optical trap

We present measurements of interspecies thermalization between ultracold samples of $^{133}$Cs and either $^{174}$Yb or $^{170}$Yb. The two species are trapped in a far-off-resonance optical dipole trap and $^{133}$Cs is sympathetically cooled by Yb. We extract effective interspecies thermalization cross sections by fitting the thermalization measurements to a rate equation model, giving $σ_{\mathrm{Cs^{174}Yb}} = \left(5 \pm 2\right) \times 10^{-13} \, \mathrm{cm^{2}}$ and $σ_{\mathrm{Cs^{170}Yb}} = \left(18 \pm 8\right) \times 10^{-13} \, \mathrm{cm^{2}}$. We perform quantum scattering calculations of the thermalization cross sections and optimize the CsYb interaction potential to reproduce the measurements. We predict scattering lengths for all isotopic combinations of Cs and Yb. We also demonstrate the independent production of $^{174}$Yb and $^{133}$Cs Bose-Einstein condensates using the same optical dipole trap, an important step towards the realization of a quantum-degenerate mixture of the two species.

physics.atom-ph↗

arXiv2017

Superballistic center-of-mass motion in one-dimensional attractive Bose gases: Decoherence-induced Gaussian random walks in velocity space

We show that the spreading of the center-of-mass density of ultracold attractively interacting bosons can become superballistic in the presence of decoherence, via single-, two- and/or three-body losses. In the limit of weak decoherence, we analytically solve the numerical model introduced in [Phys. Rev. A 91, 063616 (2015)]. The analytical predictions allow us to identify experimentally accessible parameter regimes for which we predict superballistic spreading of the center-of-mass density. Ultracold attractive Bose gases form weakly bound molecules; quantum matter-wave bright solitons. Our computer-simulations combine ideas from classical field methods ("truncated Wigner") and piecewise deterministic stochastic processes. While the truncated Wigner approach to use an average over classical paths as a substitute for a quantum superposition is often an uncontrolled approximation, here it predicts the exact root-mean-square width when modeling an expanding Gaussian wave packet. In the superballistic regime, the leading-order of the spreading of the center-of-mass density can thus be modeled as a quantum superposition of classical Gaussian random walks in velocity space.

cond-mat.quant-gas↗

arXiv2016

Controlling the Rotational and Hyperfine State of Ultracold $^{87}$Rb$^{133}$Cs Molecules

We demonstrate coherent control of both the rotational and hyperfine state of ultracold, chemically stable $^{87}$Rb$^{133}$Cs molecules with external microwave fields. We create a sample of ~2000 molecules in the lowest hyperfine level of the rovibronic ground state N = 0. We measure the transition frequencies to 8 different hyperfine levels of the N = 1 state at two magnetic fields ~23 G apart. We determine accurate values of rotational and hyperfine coupling constants that agree well with previous calculations. We observe Rabi oscillations on each transition, allowing complete population transfer to a selected hyperfine level of N = 1. Subsequent application of a second microwave pulse allows transfer of molecules back to a different hyperfine level of N = 0.

cond-mat.quant-gas↗

arXiv2016

Measurement of the binding energy of ultracold $^{87}$Rb$^{133}$Cs molecules using an offset-free optical frequency comb

We report the binding energy of $^{87}$Rb$^{133}$Cs molecules in their rovibrational ground state measured using an offset-free optical frequency comb based on difference frequency generation technology. We create molecules in the absolute ground state using stimulated Raman adiabatic passage (STIRAP) with a transfer efficiency of 88\%. By measuring the absolute frequencies of our STIRAP lasers, we find the energy-level difference from an initial weakly-bound Feshbach state to the rovibrational ground state with a resolution of 5 kHz over an energy-level difference of more than 114 THz; this lets us discern the hyperfine splitting of the ground state. Combined with theoretical models of the Feshbach state binding energies and ground-state hyperfine structure, we determine a zero-field binding energy of $h\times114\,268\,135\,237(5)(50)$ kHz. To our knowledge, this is the most accurate determination to date of the dissociation energy of a molecule.

physics.atom-ph↗

arXiv2016

Difference-frequency combs in cold atom physics

Optical frequency combs provide the clockwork to relate optical frequencies to radio frequencies. Hence, combs allow to measure optical frequencies with respect to a radio frequency where the accuracy is limited only by the reference signal. In order to provide a stable link between the radio and optical frequencies, the two parameters of the frequency comb must be fixed: the carrier envelope offset frequency $f_{\rm ceo}$ and the pulse repetition-rate $f_{\rm rep}$. We have developed the first optical frequency comb based on difference frequency generation (DFG) that eliminates $f_{\rm ceo}$ by design - specifically tailored for applications in cold atom physics. An $f_{\rm ceo}$-free spectrum at 1550 nm is generated from a super continuum spanning more than an optical octave. Established amplification and frequency conversion techniques based on reliable telecom fiber technology allow generation of multiple wavelength outputs. In this paper we discuss the frequency comb design, characterization, and optical frequency measurement of Sr Rydberg states. The DFG technique allows for a compact and robust, passively $f_{\rm ceo}$ stable frequency comb significantly improving reliability in practical applications.

physics.atom-ph↗

arXiv2015

Absolute absorption on the potassium D lines:theory and experiment

We present a detailed study of the absolute Doppler-broadened absorption of a probe beam scanned across the potassium D lines in a thermal vapour. Spectra using a weak probe were measured on the 4S $\rightarrow$ 4P transition and compared to the theoretical model of the electric susceptibility detailed by Zentile et al. (2015) in the code named ElecSus. Comparisons were also made on the 4S $\rightarrow$ 5P transition with an adapted version of ElecSus. This is the first experimental test of ElecSus on an atom with a ground state hyperfine splitting smaller than that of the Doppler width. An excellent agreement was found between ElecSus and experimental measurements at a variety of temperatures with rms errors of $\sim 10^{-3}$. We have also demonstrated the use of ElecSus as an atomic vapour thermometry tool, and present a possible new measurement technique of transition decay rates which we predict to have a precision $\sim$ 3 kHz.

physics.atom-ph↗

arXiv2014

Creation of ultracold $^{87}$RbCs molecules in the rovibrational ground state

We report the creation of a sample of over 1000 ultracold $^{87}$RbCs molecules in the lowest rovibrational ground state, from an atomic mixture of $^{87}$Rb and Cs, by magnetoassociation on an interspecies Feshbach resonance followed by stimulated Raman adiabatic passage (STIRAP). We measure the binding energy of the RbCs molecule to be $h c \times 3811.576(1)$ cm$^{-1}$ and the $|v''=0, J''=0>$ to $|v''=0, J''=2>$ splitting to be $h \times 2940.09(6)$ MHz. Stark spectroscopy of the rovibrational ground state yields an electric dipole moment of 1.225(3)(8) D, where the values in parentheses are the statistical and systematic uncertainties, respectively. We demonstrate that a space-fixed dipole moment of 0.355(2)(4) D is accessible in RbCs, which is substantially higher than in previous work.

physics.atom-ph↗

arXiv2014

Feshbach resonances, molecular bound states and prospects of ultracold molecule formation in mixtures of ultracold K and Cs

We consider the possibilities for producing ultracold mixtures of K and Cs and forming KCs molecules by magnetoassociation. We carry out coupled-channel calculations of the interspecies scattering length for $^{39}$KCs, $^{41}$KCs and $^{40}$KCs and characterize Feshbach resonances due to s-wave and d-wave bound states, with widths ranging from below 1 nG to 5 G. We also calculate the corresponding bound-state energies as a function of magnetic field. We give a general discussion of the combinations of intraspecies and interspecies scattering lengths needed to form low-temperature atomic mixtures and condensates and identify promising strategies for cooling and molecule formation for all three isotopic combinations of K and Cs.

physics.atom-ph↗

arXiv2014

Entangling two distinguishable quantum bright solitons via collisions

The generation of mesoscopic Bell states via collisions of distinguishable bright solitons has been suggested in Phys. Rev. Lett. 111, 100406 (2013). Here, we extend our former proposal to two hyperfine states of 85Rb instead of two different atomic species, thus simplifying possible experimental realisations. A calculation of the $s$-wave scattering lengths for the hyperfine states $(f,m_f)=(2,+2)$ and $(3,+2)$ identifies parameter regimes suitable for the creation of Bell states with an advantageously broad Feshbach resonance. We show the generation of Bell states using the truncated Wigner method for the soliton's centre of mass and demonstrate the validity of this approach by a comparison to a mathematically rigorous effective potential treatment of the quantum many-particle problem.

cond-mat.quant-gas↗

arXiv2013

Production of optically trapped $^{87}$RbCs Feshbach molecules

We report the production of $^{87}$RbCs Feshbach molecules in a crossed-beam dipole trap. A mixture of $^{87}$Rb and $^{133}$Cs is cooled close to quantum degeneracy before an interspecies Feshbach resonance at 197\,G is used to associate up to $\sim5000$ molecules with a temperature of $\sim300$\,nK. The molecules are confined in the dipole trap with a lifetime of 0.21(1)\,s, long enough for future experiments exploring optical transfer to the absolute ground state. We have measured the magnetic moment of the Feshbach molecules in a magnetic bias field range between 181 and 185\,G to demonstrate the ability to control the character of the molecular state. In addition we have performed Feshbach spectroscopy in a field range from 0 to 1200\,G and located three previously unobserved resonances at high magnetic fields.

physics.atom-ph↗

arXiv2013

New Determination of Muonium-Deuterium 1S-2S Isotope Shift

We report a new determination of muonium 1S-2S transition frequency and its isotope shift with deuterium by recalibrating the iodine reference lines using an optical frequency comb. The reference lines for the muonium and deuterium 1S-2S transitions are determined with a precision of 2.4*10^-10 and 1.7*10^-10 respectively. A new muonium-deuterium 1S-2S isotope-shift frequency is derived from these references to be 11 203 464.9(9.2)(4.0) MHz, in agreement with an updated bound-state quantum-electrodynamics prediction based on 2010 adjustments of Committee on Data for Science and Technology and 2.3 times better in the systematic uncertainty than the previous best determination.

physics.atom-ph↗

arXiv2013

Generating mesoscopic Bell states via collisions of distinguishable quantum bright solitons

We investigate numerically the collisions of two distinguishable quantum matter-wave bright solitons in a one-dimensional harmonic trap. We show that such collisions can be used to generate mesoscopic Bell states which can reliably be distinguished from statistical mixtures. Calculation of the relevant s-wave scattering lengths predicts that such states could potentially be realized in quantum-degenerate mixtures of 85Rb and 133Cs. In addition to fully quantum simulations for two distinguishable two-particle solitons, we use a mean-field description supplemented by a stochastic treatment of quantum fluctuations in the soliton's center of mass: We demonstrate the validity of this approach by comparison to a mathematically rigorous effective potential treatment of the quantum many-particle problem.

cond-mat.quant-gas↗

arXiv2012

Feshbach resonances in ultracold 85Rb

We present 17 experimentally confirmed Feshbach resonances in optically trapped 85Rb. Seven of the resonances are in the ground-state channel (f,m_f) = (2,+2)+(2,+2), and nine are in the excited-state channel (2,-2)+(2,-2). We find a wide resonance at high field in each of the two channels, offering new possibilities for the formation of larger 85Rb condensates and studies of few-body physics. A detailed coupled-channels analysis is presented to characterize the resonances, and also provides an understanding of the inelastic losses observed in the excited-state channel. In addition we have confirmed the existence of one narrow resonance in a (2,+2)+(3,+3) spin mixture.

physics.atom-ph↗

arXiv2012

Feshbach spectroscopy of an ultracold mixture of $^{85}$Rb and $^{133}$Cs

We report the observation of interspecies Feshbach resonances in an optically trapped mixture of $^{85}$Rb and $^{133}$Cs. We measure 14 interspecies features in the lowest spin channels for a magnetic field range from 0 to 700 G and show that they are in good agreement with coupled-channel calculations. The interspecies background scattering length is close to zero over a large range of magnetic fields, permitting the sensitive detection of Feshbach resonances through interspecies thermalisation. Our results confirm the quality of the Rb-Cs potential curves and offer promising starting points for the production of ultracold polar molecules.

physics.atom-ph↗

arXiv2007

A heated vapor cell unit for DAVLL in atomic rubidium

The design and performance of a compact heated vapor cell unit for realizing a dichroic atomic vapor laser lock (DAVLL) for the D2 transitions in atomic rubidium is described. A 5 cm-long vapor cell is placed in a double-solenoid arrangement to produce the required magnetic field; the heat from the solenoid is used to increase the vapor pressure and correspondingly the DAVLL signal. We have characterized experimentally the dependence of important features of the DAVLL signal on magnetic field and cell temperature. For the weaker transitions both the amplitude and gradient of the signal are increased by an order of magnitude.

physics.atom-ph↗